Telephone system



\ Feb. 22, 1944. 5 KING ET AL Re. 22,440

TELEPHONE SYSTEM ori inai Filed Dec. 1, 195B 9 Sheets-Sheet 1 OPERA TORSTEL .EPHOHE FIG.

WET/m ATTORNEY 9' Sheets-Sheet 2 Original' Filed Dec. 1, 1938 RE. KINGWVEWORS' 0. R. MILLER ATTORNEV Feb. 22, 1944. R. E. KING ET AL 0 ITELEPHONE SYSTEM Originaij'iled Dec. 1, 1958 9 Sheets-Sheet s n I I I myl g my s a z A RE. KING Zf 0. ,9. MILLER WW W A TFORNE V Feb. 22, 1944.R K|NG 5% AL Re. 22,440

TELEPHONE SYSTEM Original Filed Dec. 1, 1938 9 Sheets-Sheet 4 93MARC/HAL [Fr M/VENTORS: 5 KING 0. R. MILLER Br A TTORNE V Feb. 22, 1944.

R. E. KING ET AL TELEPHONE SYSTEM 9 Sheets-Sheet 5 Original Filed Dec.

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RE. KING By QR. M/LLER A TTORNEV Feb. 22, 1944. R. E. KING ET ALTELEPHONE SYSTEM Original Filed Dec. 1, 1958 9 Sheets-Sheet 6 NUQ was

INVENTOR$= RE KING By OR. MILLER ATTORNEY Feb. 22, 1944. 5, K NG ET ALRe. 22,440

TELEPHONE SYSTEM Original Filed Dec. 1, 1938 9 Sheets-Sheet 'T mac/MLPOLAR/2E0 R. 5 KING 3 0/1 MILLER MVPm ATTORNEY Feb. 22, 1944. ETAL I Re.22,440

TELEPHONE- SYSTEM 9 Sheets-Sheet 8 Original Filed Dec. 1, 1958IA/VENTURE:

I MWU Q wot REK/NG B 0.5. MILLER WWW I ATTORNEY Feb. 22, 1944. R. E.(KING ETAL TELEPHONE SYSTEM Original Filed Dec. 1, 1938 9 Sheets-Sheet 9INVENr 3; RE. KING gnu LL51? ATTO Reissued Feb. 22, 1944 TELEPHONESYSTEM Ralph E. King,

Morristown, N. J., assignors to Short Hills, and ()hmer R. Miller,

Bell Telephone Laboratories, Incorporated, New York, N. Y., acorporation of New York dated July 23, 1940, Serial er 1, 1938.Application for reissue July 17 ,1942, Serial No. 451,362

Oiginal No. 2,208,765,

No. 243,347, Decemb 42 Claims.

This invention relates to telephone systems and particularly to systemscomprising toll offices and automatic switching means for completingtoll calls.

It is the object of the invention to minimize the number of manualswitching operations in.- volved in establishing toll connections, toexpedite the completion of such connections, and to more efliciently andreliably effect the transmission of directive and supervisory signals toand through the automatic switching means employed in completing desiredconnections.

This invention is a telephone system comprising toll oflices in whichautomatic switches are provided for routing incoming calls to calledtoll and local oflices, the talking conductors of one or more of thetrunk and selector circuits constituting a simplex circuit, the balancedor unbalanced condition of which is effective to control one or moredifferential, signaling relays and the resistance of which is effectiveto control one or more marginal signaling relays. According to a featureof the invention, a differential signaling relay having one windingconnected in series with one conductor of a, simplex signaling circuitand the other winding connected in series with the other winding of thesimplex circuit is operatively responsive to an unbalance in the simplexcircuit. According to another feature,

each of two polarized differential signaling relays has one winding inseries with one conductor of a simplex circuit and another winding inseries with the other conductor of the simplex circuit, one of saidrelaysbeing operatively responsive to an unbalance which causes astronger. current in one side of the simplex circuit and the other ofsaid relays being operatively responsive to an unbalance which causes astronger current in the other side of the simplex circuit.

Another feature of the invention is a toll system in which the talkingconductors of a toll route selector comprise a simplex circuit fortransmitting directive impulses from an associated incoming line to theselector, for transmitting directive or supervisory signals to asucceeding selector or trunk used in completing a desired connection,for controlling the transmission efficiency of the associated incomingline, and for controlling the release of the selector.

A further feature of the invention is an arrangement whereby theautomatically disconnected from an outgoing intertoll trunk uponcompletion of dialing, may bev reassociated with the trunk merely byreoperation of a common;

dial key without disconoperators dial, which is necting the cord fromand reconnecting the cord to the outgoing trunk circuit.

Another feature of the invention is a toll system in which an incomingline may be connected with any one of a plurality ofv trunks throughswitching means, comprising talking conductors and a signalingconductor, circuits being closed through the signaling conductor forcontrolling the transmission pads associated with the incoming linewhile the connection between the incoming line and a desired trunk isbeing established, and for transmitting supervisory signals from theconnected trunk line to the incoming line. According to this feature thewinding of a marginal relay is connected in circuit with the winding ofa normally operated relay and the signaling conductor, the normallyoperated relay being held operated while the connection of the incomingline with a desired trunk is being established, the marginal relay beingactuated upon connection of the incoming line with the trunk to shiftthe control of the transmission pads from the circuit through thesignaling conductor to a circuit including the talking conductors inparallel, the answering of the call by an operator or subscriber beingeffective to open the pad control circuit over the signaling conductorto cause the release of the nor.- mally operated relay and therebyconnect the signaling conductor to an answering supervisory relayassociated with the incoming line.

The invention will be further explained by describing the telephonesystem illustrated in the drawings which form a part of thisspecification and in which system the invention is embodied. Theinvention is, ofv course, not limited in its application to theparticular system shown in the drawings.

Referring to the drawings:

Fig. 1 shows an operators cord, Cl and position circuit PCI;

Fig. 2 shows a dial circuit DCI theposition circuit PC"! of .Fig. 1;

Fig. 3 shows outgoing jacks J I and J 2, answering jacks J3 and J4, andan outgoing trunk circuit OTI associated with jack J I;

.Fig. 4 shows a two-way trunk circuit TWTI and a composite signalingcircuit CSI connected to one. end of a toll line Ti and to the outgoingtrunk circuit OTl of Fig. 3;

Fig. 5 shows a toll route selector TSI associated with the two-way trunkcircuit TWTI of Fig. 4 an auxiliary toll route selector AS] and anincoming trunk circuit ITI associated with the answering jack J3 of Fig.3; Fig.5 also shows associated with another two-way trunk circuit TWT4,an outgoing trunk circuit T4 and composite signaling circuit CS4, allassociated with an intertoll trunk T4;

Fig. 6 shows the composite signaling circuit CS2 and two-way trunkcircuit TWT2 connected to the other end of the toll line T I;

Fig. 7 shows a toll route selector TS2 and an outgoing trunk circuit 0T2both associated with the two-way trunk circuit TWT2 of Fig. 6; Fig. '7also shows another toll route selector TS3;

Fig. 8 shows an operators cord C2 and position circuit P02, outgoingjacks J5 and J6, answering jacks J1 and J8, an auxiliary toll routeselector A82, and an incoming trunk circuit 1T2 connected to jack J7;Fig. 8 also shows an intertoll trunk T3, a composite signaling circuitCS3 and a two-way trunk circuit TWT3 connecting trunk T3 to the selectorTS3 of Fig. '7 and an outgoing trunk circuit 0T3 connecting this trunkto jack J B;

Fig. 9 shows a voice frequency signaling circuit SC5 and an associatedtwo-way trunk circuit TWT5 connected to an intertoll trunk T5, thedistant end of which is also arranged for voice frequency signaling; and

Fig. 10 shows the relation of each of Figs. 1 to 8, inclusive, to forman operative arrangement.

The system represented in the drawings in.- cludes a plurality of tolloflices, each of which comprises a toll boardwith operators positionsand cords for answering calls incoming from local manual or dialoflices, from toll subscribers lines, from community dial offices, orfrom other toll offices and for extending an incoming call to aswitching trunk leading to a called local manual or dial oiiice, to acalled toll subscribers line, to a community dial oiiice, or to anintertoll trunk. Outgoing jacks such as J l, J2 in one ofllce, and J5and J6 in a second office, connect to switching trunks, toll lines,trunks to community dial offices, and intertoll trunks. Answering jackssuch as J3, J4 in the one office, and J1 and J8 in the second ofiice,are directly connected to recording trunks, toll subscribers lines,trunks from community dial offices, and intertoll trunks. The terminalsin the banks of incoming or auxiliary toll route selectors such as TSI,TS2, TS3, TS4, ASI and AS2 are also connected to the various lines andtrunks other than the recording trunks.

The operator's positions PCI and P02 are provided with dials and dialingcircuits for controlling the operation of incoming and auxiliary tollroute selectors in other toll oflices and for controlling the operationof the usual toll train in local or community dial-ofiices. The dialcircuit DCI and trunk circuit OTI are arranged, as hereinafterdescribed, so that the dial may be reconnected to the impulse receivingrelay of the trunk circuit by the reoperation of the position dial keyWithout having first disconnected the cord from the trunk circuit. a

The intertoll trunk TI is a two-way trunk between a first and asecondoffice and is arranged for composite signaling. At one end, trunk TI isconnected to the composite, signaling circuit CSI, the two-way trunkcircuit TWTI, the outgoing trunk circuit OTI, and the incoming tollroute selector TSI; at the other end, trunk Tl is connected to thecomposite signaling circuit CS2, two-way trunk circuit TWT2, outgoingtrunk circuit 0T2, and the incoming toll route selector TS2. The two-waytrunk circuits TWTI and TWT2 also connect to terminals in the banks ofauxiliary toll route selectors ASI and AS2 so that trunk Tl may beseized either by connecting a cord Cl or C2 to outgoing jack J I or J5or by the operation of an incoming and an auxiliary toll route selector.

The composite signaling circuits CSI and CS2, the two-way trunk circuitsTWTI and TWT2, the outgoing trunk circuit OTI, the incoming toll routeselector TS2 and the incoming trunk cir cuit 1T2 are shown in detail.The outgoing trunk circuit 0T2 which is shown only in part is similar tothe outgoing trunk circuit OTI, the incoming toll route selector TSI issimilar to the incoming toll route selector TS2; and the incoming trunkcircuit ITI is similar to the incoming trunk circuit 1T2. The auxiliarytoll route selectors AS! and AS2 are similar to the toll route selectorTS2.

The intertoll trunk T4 is one of a group between the first ofiice and a.third office which is not shown in the drawings; and the intertoll trunkT3 is one of a group between the second office and a fourth ofiice, notshown in the drawings. The associated composite signaling circuits CS3and CS4, two-way trunk circuits TWT3 and TWT4, outgoing trunk circuits0T3 and GT4, and incoming toll route selectors TS3 and TS4 are similarto the corresponding circuits and selectors associated with intertolltrunks Tl The intertoll trunk T5, which is arranged for voice frequencysignaling instead of composite signaling, is one of a group between thesecond oiiice and a fifth oflice which is not shown in the drawings. Theassociated two-way trunk circuit TWT5 is a modification of the two-waytrunk circuit TWT2 of Fig. 6 to function with the voice frequencysignaling circuit SC5. The associated outgoing trunk circuit andincoming toll route selector are similar to the outgoing trunk circuit0T2 and incoming toll route selector TS2; and an operative arrangementis formed by placing Fig. 9 adjacent and to the left of Fig. 7 with Fig.8 adjacent and to the right of Fig. 7. The reference characters appliedto the relays of trunk circuit TWT5 which correspond to relays of trunkcircuit TWT2 of Fig. 6 have like tons and units digits.

The toll route selectors TSI, TS2, TS3 and TS I and auxiliary routeselectors ASI and AS2 are of the well-known two-motion step-by-steptype. For a description of the structure of such switches reference maybe had to pages 57 to 63 of the second edition of Automatic Telephony bySmith and Campbell. The switches TSI, TS3, TS4, ASI and AS2 are eachrepresented by a set of brushes and one or more sets of terminals butnone of the magnets, relays or other apparatus associated with theseswitches is shown in the drawings. The bank of the toll route selectorTS! is represented by a single set of terminals but this selector isotherwise complete with all magnets, relays and other associatedapparatus.

Assume now that a call incoming to the toll board in the first ofiice isanswered by connecting the plug RP of cord CI to an answering jacks suchas J3 or J4. The talking key TK having been operated, and the positioncircuit being idle, relay II] is operated by the energization of itsleft winding. Relay Ill closes a circuit for operating relay 20 of theposition circuit and relay 2!! closes the locking circuit through theright winding of relay II). The operators telephone is connected throughthe contacts of relay. lll'to the-calling-line or trunk. To extend theconnection, the plug F? is connected to: an outgoing jack such as J l orJ 2'; and; .ifthe connected outgoing. trunk is arranged for; dialing,as. is. the case if completion or the call includes the selectiveoperation of one or more toll route selectors or the selective operationof a toll train inalocal or community dial office, the dial key DH isoperated to its Front position. Although thcord and position circuits.Cl and'PCl are arranged so that the dial DI may be connected to eitherend of the cord, only the relays and connections necessary for dialingover the front plug FP are shown in the drawings. Assume further that onthe call in question, plug FF is connected through jack J I to theoutgoing trunk circuit OTi. A circuit is closed through the sleeveconductor of plug FF and contacts of key TK for operating relays 2| and22 of the position circuit and sleeve relay 54 of the out cuit lightingthe cord supervisory lamp FL. With the dial key DK operated and relay 23operated, relay of the dial circuit DCI operates, disconnecting the tipand ring-conductors of the plug .F-P from, the operators telephone setand closing a circuit for operating relay 25. Relay 25 closes a circuitfor lighting the dial pilot lamp DP and a circuit which includes backcontacts of relays 28, 35, 3E, and 3| for operating relay 2'5. Relay 2Ecloses a circuit forcperating relay 21. Relay 2! closes a circuit foroperating relay 2%. Relay 28 looks under control of relays 25, 35, 3Eand 3| and opens the operating circuit of relay 25.

In the outgoing trunk circuit OT], the operation of relay 54 closes acircuit foroperating relay Bil. Relay 68 locksunder control of relay 69and closes a circuit for operating relay 58. Relay 58 closes a circuitlighting the busy lamps such as BLi associated with jack .J I and otherjacks connected in multiple with jack J I; closes circuits for operatingrelays 64 and G9; closes a circuit including the inner lower contact ofrelay 18 for operatively energizing the upper winding of relay l6;closes a circuit for operating relay it; connects ground to the sleeveconductor 93 of the two-way trunk circuit TWTI disconnects the windingof relay 55 from the sleeve conductor 93: connects the winding of thesupervisory relay 55 to the front contact of the signaling relay 9!] ofthe composite signaling circuit CSI; and disconnects the front contactof signaling relay 9!) from conductor 5%: leading to the windings ofrelays tile and lei of the two-way trunk circuit TW'li. The operation ofrelay 64closes circuits for operating relays 60 and 6!, connects groundto sleeve conductor 93 and connects ground through its middle lowerfront contact, back contacts of relays i9 audit. and conductor 52 to thering conductors of jack J| and plug F19. The ground connected toconductor 33 guards against seizure of trunk Ti by atoll route selectorsuchias ASA and operates relay- |l 5. Relay H5 locks and disconnects thewindings of relays 05 and "ii from conductor 35. The operation of relay69 opens the locking circuit of relay 68, but relay 68 holds undercontrol of relay 5 It is the function. of slow-release relay 6?, andslow-to operate relay 65 to prevent the release of relay m, if operated.before the plug F? is fully seated in jack J l. The operation of relayl8=maintains the operative energization of the upper winding of relay TBindependent of relay '18. The armaturesof-sig-nal relays 90 and I90 are.normally heldin the position shown in the drawings by the energizationof the upper biasing windings of theserelays. The operation of relay "1closes a circuit from signaling battery Bl, through resistor 15, frontcontact of relay Hi, retard coil 89,. middle winding of relay 58, upperwindings of, retard coils 86, over. the upper conductor of trunk Tl,upper windings of retard coils I86, middle winding of relay I30, retardcoil I89, back contact of relay Hi), and back contacts of relays 2 I0and 2| 1 to ground. The closure of this circuit operates relay I90 andconstitutes seizure of trunk TI to effect guarding of the trunk as busyas hereinafter described. Any variation in the energization of themiddle, operating windings oi relays 90 and I9!) due to difference inground potential betweenthe oflices terminating trunk TI is compensatedby the energization of the lower, biasing-windings of these relays in aground to ground circuit through the lower conductor of trunk T5. Theoperation of relay 6|] closes contacts for holding the busy lamps BLIlighted. Relay lillalso closes a network comprising resisttors 12, I3and I4, ballast lamp II and the middle, biasing winding of relay H1. Theballast lamp has a high temperature coeiiicient of resistance andvariations in its. resistance due to variations in the voltage ofsignaling battery Bl affects the energization of the middle winding ofrelay It so as to compensate for changes in the voltage of the signalingbattery. The use of the ballast lamp, network of resistors, and biasingwinding of. relay it! to compensate for changes in the voltage of theSignaling battery BI is disclosed and claimed in Patent No. 2,174,006granted Sept. 26, 1e39, to O. R. Miller. Relay 6| closes a circuit frombattery through resistor El and the back contact of relay for holdingthe normally operated pad control relay 83. The normally closed circuitfor operating relay ilsincludes the lower back contact of relay 6!,resistor 82. and back contacts of relays H1 and iii! of the two-waytrunk circuit TWTI.

When. the circuit of slow-to-release relay 2% is opened by the operationof relay 28, as hereinbefore described, relay 28 remains operated for aninterval long enough for relay E9 of trunk circuit OTI to have beenoperated, at which time a circuit is closed for holding relay 21operated and for operating relays 29 and m. This circuit is traced frombattery through the winding of relay 2?, winding of relay 29, upperfront contact of relay 2?, upper back contact of relay 32, upper frontcontact of relay 24, inner left front contact of relay H1, contacts ofringing key RK, tip conductors-of plug FF and jack J I; conductor 5|,back contact of relay E5, winding of relay 18, to ground at a frontcontact of relay 69. The operation of relay 29 closes a circuit foroperating relay 3!. Relay 3| closes a circuit for operating relay E52,and closes a circuit from battery through resistor is, upper frontcontact of relay 3%, impulse contacts of the dial Di, winding of relaefi; back contact of relay 26, front contacts of relays Z4 and: Ill,ring conductors of plug 13? and jack J I, conductor 52, back contacts ofrelays 66 and i9, and through resistor '35 to ground at a front contactof relay 54. Relay 32 opens the circuit through the windings of relays2i and 29 and. connects thetip conductor of plug FP through resistor 33to battery to hold relay ES operated. Although relays 2'5 and 29 releaserelay 3| is held by relay 32 and relay 3?. is held under control of thedial key. Relay 3| holds relays 28 and 24.

" "The operation of relay I8 closes a circuit for operating relay I andopens the circuit through the winding of relay I5. Relay I9 locks undercontrol of relay E9 and connects the operating winding of the impulserelay I0 in series with conductor 52 and the impulse contacts of thedial DI. Since the operation of relay l8 disconnects the battery at itsinner lower back contact from the operating winding of relay I0 and therelease of relay I6 disconnects the battery at its front contact fromthis winding of relay I0, relay I0 is now ready to respond to impulsescreated by the operation of dial DI. The lower biasing winding of relayI0 is connected in series with a battery 'of the same voltage as thedialing battery so as to compensate for variations in the voltage ofthis battery.

The required toll route number is dialed and also the local office codeand number of the called subscriber if the called subscribers line is ina dial office. The impulse relay I0 repeats the dial impulses over trunkTI to relay I90 of the composite signaling circuit CS2. Each time thedial is moved elf-normal relay 31 operates to hold relays 32 and 3|operated, independent of the dial key. When dialing is completed, key DKis restored and relay 3? releases; relays 32, EI, 24 and 25 release insuccession and the plug FF is thereby reconnected to the operatorstelephone set. While the talking key TK is operated, supervisory signalsare received over the sleeve conductor of plug FP by the marginal relay22 and relay 22 controls the supervisory lamp FL. When the talking keyTK is restored to normal relays II), 20, 2|, 22 and 23 are released andthe lamp FL is controlled through the sleeve conductor of. plug FP bythe supervisory relay 55 of the trunk circuit OTI. The release of relay32 opens the circuit through resistor 33 and the tip conductor of plugFP to cause the release of relay I0 and thereby reconnect batterythrough the lower contact of relay E8, to hold relay 10, before therelease of relay 3i opens the dialing circuit, relay 3| being slow inreleasing. vThe release of relay It! closes circuits including a frontcontact of relay I9 for operating relay 69 and reoperating relay I6.Relay 65 disconnects conductors and 52 from the winding of relay I3 andcontacts of relay I9, opens the circuit through resistor 61 and relay83, and connects conductors 5i and 52 through the windings of retardcoil 00, and front contacts of relay 5!, through windings of relays 61%and TI in parallel, thence through the winding of pad control relay 83to ground. The pad control relay 83 is thereupon held operated in serieswith resistors II and E2 of the position circuit PC! long as the talkkey of cord CI is operated. After the talk key is restored and relay I0releases, the pad control relay 83 is controlled through the tip andring conductors of the calling line or trunk with which plug RPisconnected; if under this condition relay 83 releases, relay 34operates to short-circuit the transmission pads PI and P2. Relay 56 alsoopens the normally connected voice frequency repeater terminationcomprising a resistor and condenser and a back contact of relay 56.

The aforementioned operation of relay I90 upon seizure of the outgoingtrunk circuit OTI closes a circuit from ground through the front contactof relay I90, back contacts of relays I58 and I60 of outgoing trunkcircuit 0T2, conductor I95, back contact of relay 2I5 of two-way trunkcircuit TWT2, back contact of relay 202, to the winding of relay 200.Relay 200 operates, disconnecting relay 2I5 from conductor I93,connecting ground to conductor I93 to guard trunk TI from seizure by atoll route selector such as AS2, and operating relay I55 of the outgoingtrunk circuit 0T2. Relay I56 connects battery to the sleeve of theoutgoing jacks J5 so as to make these jacks test busy and closes acircuit for operating relay I60. Relay IEO closes a circuit for lightingthe busy lamps BL5. Although relay I50 opens the normally closedconnection between front contact of relay I and conductor I95, relay I59maintains a connection between the front contact of relay I90 andconductor I so as to hold relay 200 operated, Relay 200 also closes acircuit for operating relay 20I of twoway trunk circuit TWT2 and relay225 of toll route selector TSZ. This circuit is traced from ground atthe front contact of relay I 90, back contact of relay I58, frontcontact of relay I56, conductor I 95, back contact of relay 2I5, windingof relay 20 I, back contact of relay 2 I B, winding of marginal relay206, front contact of relay 200,-

thence in simplex through both windings of differential relay 205, backcontacts of relay IBI, windings of retard coil I 80, conductors IOI andI82, front contacts of relay 200, conductors 22! and 222, back contactsof relay 229 of selector T82, and through resistors 23I and 232 to andthrough resistor 230 and a back contact of relay 229 to the winding ofrelay 225. Relay 206 does not operate because it is marginal and relay205 does not operate because its windings are differentially energized.The operation of relay 20I causes the operation of slow-to-release relay202. After relay 2532 operates, relay 200 is held operated throughresistor 204 to ground at front contacts of relays 20I and 292. Relay2&2 connects ground from the back contact of relay M6 to the sleeveconductor 223 of selector TS2 so as to con trol the release of thisselector as hereinafter described. Relay 2I9 is normally operated inseries with the upper winding of relay 201 and in series with resistor203 in parallel with resistor 22!] of selector TSZ. The connectionbetween the winding of relay 26.9 and resistor 220 includes a frontcontact of relay 2 I9, conductor 224, contacts of the 11th rotary stepsprings, and a back contact of relay 229. Relay 201 is marginal and isnot normally operated. After relay 2B2 operates, relay H9 is held.operated in series with resistor 220 until relay 229 operates ashereinafter described. The operation of relay 225 closes a circuit foroperating the slow-to-release relay 220. Relay 226 connects ground tothe sleeve conductor' '223 and also connects ground through its outerlower front contact to an alarm circuit so that an alarm will beactuated in case no impulses are received by relay 225 within apredetermined interval of time.

When the calling operator dials the first digit of the toll routenumber, the impulses are repeated by relay I0 of the outgoing trunkcircuit OTI over the tip conductor of trunk TI to relay I90 of thecomposite signaling set CS2. The release and reoperation of relay I90 inresponse to each impulse causes a corresponding release and reoperationof relays 20! and 225. Being slow in releasing, relays 202 and 22Sremain operated during the response of relays 29I and 225 to the dialimpulses. The release of relay 225 in response to the first impulsecloses a circuit for operating the vertical stepping magnet 233 and theslowto-release relay 221. The operation of magnet 233 raises the brushesone step The vertical off-normal springs VON are actuated as soon as theshaft of the switch moves out of normal 110? sition closing a circuit,which includes the front contact of relay 227, for operating relay 228.The reoperation of relay 225 at the end of the first impulse causes therelease of stepping magnet 233. The release and reoperation of relay 225in response to each succeeding impulse of the train effects acorresponding operation and release of stepping magnet 233, therebystepping the brushes up to the level corresponding to the digit dialed.When relay 225 remains operated after receiving the last impulse of theseries created by the dialing of the first digit of the toll routenumber, relay 22'! releases, opening the operating circuit for relay 223and closing a circuit for operating the rotary-stepping magnet 234.Relay 228 is held operated through its upper front contact until magnet2534 operates. The operation of magnet 234 steps the brushes intoengagement with the first set of'terminals in the level selected inresponse to the dial impulses. The release of relay 228 causes therelease of magnet 234. If this set of terminals is busy, the test brush231 encounters a ground potential which is effective to cause thereoperation of relay 228, the winding of relay 228 being connectedthrough contacts of the VON springs, the back contact of magnet 234, anda back contact of relay 229 to brush 231. The reoperation of relay 228causes the reoperation of magnet 234 to step the brushes to the next setof terminals. The operation of magnet 234 again causes the release ofrelay 223 and the release of relay 228 causes the release of mag,- net234. This cycle of operations is repeated to advance the brushesstep-by-step until test brush 231 encounters a terminal which is notmarked by ground potential connected thereto. whereupon relay 229 isoperated by the current in a circuit from battery through the Winding ofrelay 228, contacts of the VON springs, back contact of magnet 234,winding of relay 229, nor mally closed contact of the 11th rotary stepsprings, to ground on sleeve conductor 223. Being marginal, relay 228does not operate in series with relay 229. Relay 229 disconnects relay225 from the conductors 22I and 222 and connects these conductorsthrough brushes 235 and 236 to the line relay, which is not shown in thedrawing of the auxiliary toll route selector A52. The ground potentialconnected through the back contact of relay 2S6 and upper front contactof relay 222 to sleeve conductor 223 is extended through a front contactof relay 229 to the test brush 231 to mark the selected auxiliary tollroute selector as busy and thereby prevent its seizure by any other tollroute selector having access thereto. Relay 225 releases causing therelease of relay 22B; and relay 223 disconnects ground from the alarmcircuit. The operation of relay 223 disconnects resistor 22%! fromconductor 224 and connects conductor 224 through brush 233 to selectorcircuit A82 in which there is a connection through a resistor similar toresistor 223 to hold relay 219 operated.

It is assumed that the desired toll route number is a two-digit numberin which case there are no intermediate selectors between selector TS2and selector AS2. If a large number of toll routes is required therewill be one or more additional selectors in the train required forselecting a desired toll route; and if one selector is sumcient theselector TS2 will have direct access to the groups of trunks, which inthe system shown, are connected to the banks of the auxiliary selectorsASZ. Upon the dialing of the second digit of the toll route number, theauxiliary toll route selector AS! is directively operated :to select adesired group of trunks and automatically operated to seize an idletrunk inthe'selected group. The selector A82 may have access to trunksto local ofiices, either manual 'or dial, to toll lines extending totoll subscribers or to other toll offices, to incoming trunk circuitssuch as 1T2 terminating at'the positions 'of a toll boa-rd, and togroups of intertoll dialing trunks,- One of-such groups beingrepresented by trunk TI and another by trunk T3.

Assume that the dialed toll route number effects the operation ofselectors T82 and AS2 to select the incoming trunk circuit 1T2terminating in a jack J l at an operators position comprising a cord C2andposition circuit PC2. Relay 2M of two-way trunk circuit TWT2 is heldoperated and relay 25l of the incoming trunk circuit 1T2 is operated bythe current in a circuit fr'omrground through the front contact of relaylSl'Lback contact of relay I58, front contact of relay 1'53, conductorI25, back contact of relay 2|5, winding of relay 23L back contact ofrelay 2l6,'windin'g of relay 206, front contact of relay 200, thence insimplex through both windings of relay 205, back-contacts of relayIBL'both windings of retard coil MEL-conductors I81 andIBZ, frontcontacts of relay 222, conductors HI and 222, front contactsoirelay'229,brushes 235 and 238, through the selector ASZ, conductors 24I and 242,both windings of retard coil 245, and through resistors 24B, 24B and 249to the Winding of relay 25!. The resistors 243, 248 and249 are so chosenthat the current through one side of the simplex is enough stronger thanthe current through the other side of the simplex to cause the operationor differential relay 205; but relay 205 is almost immediately releasedbecause-the simplex is balanced as soon as the normally operated relayZll releases due to the operation of relay2-56 as here-' inafterdescribed. The current in thesimplex circuit is not strong enough tooperate marginal relay 206. Relay 25i closes a circuit for lightinganswering lamp ALT, connects the source of ringing current 250 throughcondenser 275 to talking conductor 2522, thereby 'transmitting'ringingtone to'the calling operator to indicatethat an operator is beingsignaled. 'At the same time that the simplex circuit is closed foroperating relay 25!, a circuit is closed for holding relay 2 I 9operated, for operating marginal relay 201 of the two-way trunk circuitTWT2, and for operating relay 256 of'the incoming trunk circuit IT2;thiscircuit is traced from ground through the upper winding of relay 201,Winding and front contact of relay '2i9, conductor'224, back contact ofthe 11th rotary step springs of selector TSZ, front contact of relay22.9, brush 238, through selector AS2, conductor 244, back contact ofrelay 214 and the lower winding ofrelay 256. 'Relay201 locks through itslower winding and a front contact of relay 2B2. Relay 256 locks throughits upper winding to the holding ground connected to conductor 243 from.the back contact of relay 216 of the two-way trunk circuit TRT2.Normal1yrelay-2H isheld operated in a circuit including resistors266,261, 268 -and 269 and the winding of relay-2 lll v 0nd including theback contact of'relay 256. Although-relay 21! is shown as a polarizedrelay, it may be a sensitive nonpolarized relay. When relay 2'56operates, relay 21I releases, thereby opening the short circuit aroundresistor 241 and closing a short circuit around resistor 248 so as tobalance the simplex circuit and cause the release of relay 205. Withrelay 205 released and relay 201 operated, relay I83 releases, and relayI84 operates shortcircuiting pads PI and P2. I

When a plug of a cord C2 is inserted in jack J1 to answer the incomingcall, relay 212 is ope-rated since there is battery connected to thesleeve of the plug, the cord C2 and position circuit PCZ being similarto cord CI and position circuit PCI shown in Fig. 1. Relay 212 closes acircuit for operating relay 213. Relay 213 closes a circuit, whichincludes a front contact of relay 25I, for operating relay 214. Relay213 also disconnects the repeater termination comprising condenser 216and resistor 211 from conductor 25L This termination, normally connectedacross conductors 26I and 262, prevents the voice-current repeater of aconnected intertoll trunk from singing prior to answer of a call byanoperator. Relay 214 looks to the ground connected to sleeve conductor243, opens the ringing tone connection, extinguishes lamp AL1,disconnects the supervisory conductor 244 from the operating winding ofrelay 256, and connects this conductor in series with a back contact ofrelay 210 to ground at a front contact of relay 213, thereby causing therelease of relay 2I9 of two-way trunk circuit TWT2. The release of relay2l9 disconnects its winding from conductor 224 and connects thisconductor through the upper back contact of relay 2| 5, to the windingof the answering supervisory relay 2. Relay 2 cperates therebyconnecting battery through resistor I15, front contact of relay 2, theback contacts of relays 2") and I10, and retard coil I89 to the windingsof relay I90 thereby causing the operation of relay 90 at the other endof trunk TI. Relay 90 closes a circuit .for operating supervisory relay55. Relay 55 opens the circuit through the low-resistance, lower Windingof relay 54. Since the upper winding of relay 54 is a high-resistancewinding, the current in the circuit through the sleeve conductor of plugFF and lamp FL is reduced to extinguish lamp FL to indicate to thecalling operator that the call has been answered.

The pad control relay 21I is held operated in a simplex circuit throughthe conductors 2Iil and 262 to battery, through pad control resistorssimilar to resistors II and I2 of position circuit P01, in the operatorsposition circuit P02 as long as the talking key of cord C2 is operated.When the connection is extended through the other end of cord C2 to atrunk or line and the talking key of cord C2 is restored to normal,relay 21I is controlled by the trunk or line to which the other end ofcord C2 is connected. If the connected trunk is a local trunk or otherlow-loss line, relay 21I is held operated in the circuit through cord C2and pad control resistors in the connected trunk or line, similar to thepad control resistors in the operator's position circuit. If theconnected trunk is an intertoll trunk or other high-loss line, relay 21Ireleases since the connected trunk or line circuit is not provided withpad control resistors and the impedance in series with the winding ofrelay 21I is infinite. the simplex circuit to cause the reoperation ofrelays 205 and I83 and release of relay I84 there- If relay 21Ireleases, it unbalances by opening the short circuit around pads P3 andP4. If relay 21I is held operated, the simplex is balanced, relays 205and I83 are not operated, and relay I84 short-circuits the pads P3 andP4.

The calling operator can recall the answering operator by operating theringing key to the lower position to connect signaling battery to thetip conductor of plug FP, the battery having a high enough voltage, forinstance 45 to 50 volts, to operatively energize the winding of relayB3. Relay 63 closes a circuit for operating relay 59 and a circuit forholding relay operated.

When the ringing key is restored to normal relay 63 releases. Afterrelay 63 releases and before the slow-to-release relay 59 releases,relay 10 releases thereby temporarily transferring the upper signalingconductor of trunk TI from battery to ground to cause the release andreoperation of relay I90. The release and reoperation of relay I causesthe release and reoperation of relays 20] and 25I. Being slow inreleasing, relay 202 remains operated. The release of relay 25I causesthe operation of relay 252. Relay 252 connects the low-resistancewinding of relay 254 in parallel with the high-resistance winding ofrelay 212, thereby causing the cord supervisory lamp (not shown) tolight. Relay 254 operates and locks. When relay 25I reoperates, relay252 releases and interrupter I is connected to the winding of relay 251.Relay 251 is alternately operated and released times a second under thecontrol of interrupter I. Each time relay 251 operates, it closes aholding circuit for relay 254 and disconnects the low-resistance windingof relay 254 from the sleeve conductor 263 so that the cord supervisorylamp is extinguished. The cord lamp is thus flashed to signal theoperator until the talking key of the cord is operated to answer therecall. When the talking key is operated, marginal relay 254 releasesbut relay 212 remains operated. The release of relay 254 disconnects thewinding of relay 251 from interrupter I.

If the answering operator wishes to signal the calling operator,operation of the ringing key connects battery of a high enough voltageto conductor 26I to operate the marginal relay 210. While the ringingkey and relay 210 are operated, ground is disconnected from conductor244 releasing relay 2. The release of relay 2 causes the successiverelease of relays 90 and 55 at the calling end of trunk TI. Relay 55reconnects the low-resistance lower Winding of relay 54 in parallel withthe high-resistance upper winding to light the lamp FL of cord CI torecall the operator.

If the answering operator disconnects cord C2 from trunk circuit 1T2while the calling cord C I remains connected with outgoing trunk circuitOTI, relays 212 and 213 release. Relay 213 reconnects condenser 216 andresistor 211 across conductors 26I and 262, disconnects ground fromconductor 244 to release relay 2 and thereby signal the calling operatoras described in the preceding paragraph, and closes a circuit foroperating relay 255. Relay 255 connects battery to both windings ofretard coil 245, the current through the winding of marginal relay 206of the two-way trunk circuit TWT2 being increased sufficiently to causeits operation. Relay 206 closes a circuit for operating relay 2I6; andrelay 2| 5 looks under control of relay 202. The operation of relay 2I6disconnects ground from conductor 223, thereby causing the release ofrelay 229 of selector TS2, the release of the corresponding relay inselector A82, and the release of relays 256 and 2% of incoming trunkcircuit 1T2. The release of relay 229 closes a circuit for operatingrelease magnet 239 and the shaft and brushes of selector TS2 arethereupon restored to normal. The opening of the upper contacts of theVON springs, when the shaft reaches normal position, releases the magnet239. The shaft and brushes of selector ASZ are restored to normal inlike manner. The aforementioned operation of relay 2|6 causes therelease of relays 20|, 205 and 206 but holds relay 200 operated. Relay2|6 also closes a circuit for holding relay 2| I. The release of relay20| causes the release of relay 202; and relay 292 releases relays H6and 2. The release of relay 2 again causes the lighting of lamp FL ofcord Cl and the release of relay 2|B recloses the circuit hereinbeforedescribed for perating relays 20| and 205 and reiay 225 of selector TSZ.Relay 20| again closes the circuit for operating relay 202; and relay202 reconnects ground from the back contact of relay 2|6 to conductor223. The calling operator may now reconnect the dial to cord CI andreoperate selector TS2 and succeeding switches to complete another callwithout trunk Tl having been released between calls. By reoperating thetalking key TK, relays I0, 20, 2|, 22 and 23 are reoperated; and byreoperating the dial key DK, relays 24, 25, 25, 21 and 28 arereoperated. The operation of relay 28 causes the release of relay 26;relay 2'! holds and relay 29 operates through the tip conductor of plugFP in series with the windings of relays 63 and 83. Relay 63 is marginaland does not operate in this circuit since the Voltage of the batteryconnected to the winding of relay 2! is only a 24=-volt battery. Theoperation of relay 29 causes the successive operation of relays 3| and32 and the release of relay 2! thereby again connecting battery throughresistor 34 to the ring conductor of plug FP, thence through conductor52, front contact of relay 8%, lower Winding of retard coil 80, frontcontact of relay 6|, lower winding of relay ll and Winding of relay 83to ground. Relay 11 operates and locks through its upper winding undercontrol of relays I9 and 18. The operation of relay ll causes therelease of relay 65. Relay 66 again closes the circuit from batterythrough resistor 33 and the tip conductor of plug FP for operating relay'58. With relay l3 operated, the upper operating winding of relay i isunder the operative control of the impulse contacts of the dial DI andthe dialing of another toll route number results in the reoperation ofselector T82 and an auxiliary selector AS2 as above described.

When the calling operator disconnects cord Cl from trunk OTI, relay 54releases. Relay 54 releases relay 53. Relay 68 releases relay 58. Relay58 releases relays I0, 64 and 69 and also relays 55 and it, it operated.Relay 64 releases relays 60 and ti. Relay E9 releases relays I9 and alsorelay 18, if operated. The release of relay lb disconnects signalingbattery BI from the upper signaling conductor of trunk Tl therebycausing the release of relay I90. The release of relay It!) opens thecircuit through the wind ing of relay 2M causing its release, therelease of relay 2%, if operated, and the release of relay 25| of trunkcircuit 1T2, if trunk TI has been extended to trunk 1T2, Or the releaseof relay 225 if trunk Ti is extended only to selector TSZ, or therelease of the line relay of any other selector, trunk or toll line withwhich trunk TI is connected. The release of relay 20| causes the releaseof relay 202. The'release of relay 202 causes the release of relay 200,the release of relay 201, if operated, and th reoperation of relay 2|9.Relay 202 also disconnects ground from conductor 223, causing therelease of relay 229 of selector T552, the release of the correspondingrelay of selector A82, and the release of relays 255 and 274 on aconnection to trunk circuit 1T2. The release of relay 229 causes thereturn of selector T82 to normal as hereinbefore described. Relays 272and 213 remain operated until cord C2 is disconnected from jack Jl.

If during the dialing of a toll route number, a toll route selector suchas T82 or ASZ or a selector of a toll train in a local dial ofiice towhich the connection is extended encounters an all-trunks-busycondition, relay '55 is alternately operated andv released to flash lampFL. Assuming it is selector T82 which finds all trunks busy in aselected level, the 11th rotary step springs are actuated, disconnectingthe winding of relay 229 from conductor 223, disconnecting conductor.224 from resistor 220 to release relay Eiil, and connecting interrupterI to conductor 22 to cause the intermittent operation of relay 2| i.Relay 2! causes the alternate operation and release of relay and relay90 in turn causes the alternate operation and release of relay 55 toflash lamp FL. If the selector which encounters an. all-trunks-busycondition is arranged to camp on the busy level and wait for a trunk tobecome idle, relays 98 and 55 are alternately operated and released insimilar manner but at a different rate. The operation of relay 55 causesthe operation of relay 51 and relay 5! locks through a back contact ofrelay E5 to ground at a front contact of relay 69. Relay 51 connectsbattery to the operating Winding of relay [0 to prevent its furtherrelease under control of the impulse contacts of dial 1) so that furtherimpulses will not be sent out over trunk T in case another digit isdialed before the operator takes notice of the camp-on signal. Theoperator thereupon restores the talking and dial keys to normal causingthe release of relay l8 and operation of relays 66 and F5. The operationof relay E36 release relay 5'1 and relay iii holds relay i0 operated. Aselector arranged for campon operation is disclosed in Patent No.2,097,165, granted to R. L. Stokely October 26, 1937. When a trunkbecomes idle, the signal is changed and operation of the talking anddial keys causes the reassociation of the dial With trunk OT! ashereinbefore described. The dialing of the digit 1 will then beeffective to send one impulse to the selector in question and thus startits trunk hunting operation. Any additional digits of the toll routenumber may then be dialed and relay 10 will repeat the dial impulses.

Since the trunk TI may be seized by toll route selectors such as ASl atone end and A552 at the other end, it is necessary that the two-Waytrunk circuits TWT! and TWT2 and outgoing trunk circuits OT! and GT2 bearranged to establish the busy conditions which prevent seizure byanother selector or by an operator and to establish the required padcontrol and through signaling conditions. To illustrate theseoperations, assume that a trunk T3 is seized by a toll operator in athird office. The associated composite signaling circuit CS3, two-waytrunk circuit TWTS, outgoing trunk circuit 0T3 and incoming toll routeselector T33 are similar to the corresponding circuits CS2, TWT2, 0T2and T62 associated with trunk TI and the operations re sulting fromseizure of trunk T3 and dialing are similar to those hereinbeforedescribed on the call incoming over trunk TI. Assume further that theincoming toll route selector TS3 is operated to select an auxiliar tollroute Selector AS2 and that the selector AS2 is operated to select thetrunk TI. Upon extension of the connection from trunk T3 through thebrushes of selector A52 to conductors I9I, I92, I93 and I94, holdingground potential is connected to conductor I93, ground from the frontcontact of the signaling relay in the composite signaling circuit CS3 isconnected to conductors I9I and I92, and ground through the windings ofrelays in circuit TWT3 corresponding to relays 207 and 2I9 in circuitTWT2 is connected to conductor I94 all in similar manner to theconnection of ground to conductors 24I, 242, 243 and 244 of incomingtrunk circuit IT2 on the call hereinbefore described. The connection ofground potential to conductor I93 closes circuits for operating relay2I5 of the two-way trunk circuit TWT2 and relay I56 of the outgoingtrunk circuit T2. Relay 2I5 locks to conductor I93, connects relay 2I8to conductor I95 and disconnects the windings of relays 200 and 20I fromconductor I95. Relay I56 connects battery to the sleeve of jack J5 as abusy condition and operates relay I60. Relay IEO closes a circuit forlighting the busy lamps BL5. The connection of ground potential from thefront contact of the signaling relay of circuit CS3 through circuitsTWT3, TS3 and A82 to conductors I9I and I92, is extended through backcontacts of relay 200, conductors I8I and I 82, windings of retard coilI80, back contacts of relay I6I, windings of relay 205, conductor I96,and back contact of relay 200 to the operating winding of relay 2I0. Theconnection of ground to conductor I94 causes the operation of relay 2I'Iof two-way trunk circuit TWT2 and relay 2I'I locks through its upperwinding to the holding ground on conductor I93.

The operation of relay 2I0 disconnects ground from and connects batterythrough resistor I I5 to retard coil I89 thereby causing the operationof the signaling relay 90 at the other end of trunk TI. The operation ofrelay 90 connects ground to conductor 95 to cause the operation ofrelays I00. IOI, I02 and I05 of two-way trunk circuit TWTI and theoperation of the line relay (not shown) of selector TSI. Relay I00connects ground to conductor 93 to guard two-way trunk circuit TWTI fromseizure by an auxiliary toll route selector such as ASI. The connectionof ground to conductor 93 also causes the successive operation of relays56 and 60. Relay 56 connects battery potential to the sleeve of jacks JI to mark this trunk as busy and relay 60 closes the circuit forlighting busy lamps BLI. The connection between ground at the frontcontact of signaling relay 90 and conductor 95 is maintained by a, frontcontact of relay 56, although the normal connection is opened at theback contact of relay 60. Relay 55 also opens the repeater termination,comprising a condenser and resistor normally connected across conductors8| and 82 to prevent the associated voice frequency repeater which isnot shown in the drawing from singing. The operation of toll routeselector TSI and an auxiliary selector ASI is similar to that ofselector TS2 hereinbefore described. The aforementioned operation ofrelay 2II causes the release. of relay I83 and the operation of relayI84 to short-circuit pads P3 and P4. Answering supervision is receivedover trunk TI by relay I90. The operation of relay called Subscriber inthe local oflice answers.

I closes a circuit including a front contact of relay 2I5 for operatinrelay 2IB. Relay 2I8 opens its operating circuit, locks to ground onconductor I93 and opens the operating circuit of relay 2I'I. With relays2I5 and 2I8 operated, the connection of ground through the front contactof relay I90 and conductor I95 is extended through conductor I94,selectors A82 and T53 through back contacts of the relays in two-waytrunk circuit TWT3 which correspond to relays 2I9 and 2I5 of circuitTWT2 to the winding of the relay which corresponds to relay 2| I,thereby transmitting the answering supervisory signal over trunk T3 tothe calling operator.

0n calls incoming over trunk TI and extended through selectors TS2 andA52 to a switching trunk leading to a local oifice, there is no relay inthe outgoing trunk circuit of the switching trunk corresponding to relay256 of incoming trunk circuit 1T2 and therefore relay 2I9 of twowaytrunk circuit TWT2 releases as soon as selector AS2 seizes the switchingtrunk. The release of relay 2I9 connects conductor 224 to the winding ofrela 2 to operate this relay when the On such a. call, relay 201 is notoperated and pad control relay I83 is held operated so that the pads P3and P4 remain in the talking circuit.

on a call incoming over trunk TI and extended through selectors TS2 andAS2 to trunk T3, the pad control and supervisory operations are similarto those on a call incoming over trunk T3 and extended through selectorsTS2 and AS2 to trunk TI While the two-way trunks TI and T3 are shown anddescribed as being arranged for composite signa1ing it is of courseunderstood that any type of signaling may be employed. For instance inthe arrangement shown in Fig. 9, an intertoll trunk T5 terminates in asignaling circuit S05 arranged for voice frequenc signaling and. theassociated two-way trunk circuit TWT5 is provided with two polarizeddifferential relays controlled in a simplex circuit comprising thetalking conductors in parallel. One of these two relays is operated byan unbalance of the simplex which causes a larger current in one side tocontrol the transmission pads and the other relay is operated by anunbalance of the simplex which causes a larger current in the other sideto control the repeating of the incoming voice frequency implses inaccordance with the type of signaling provided in the outgoing trunk orline to which the connection is extended. In the following descriptionit is assumed that the trunk T5, signaling circuit SC5, and two-waytrunk circuit TWT5 are associated with an outgoing trunk circuit and atoll route selector similar to the trunk circuit 0T2 and selector TS2shown in Fig. '7.

When the trunk T5 is seized at its distant end and voice frequencysignalin current is transmitted over trunk T5 as a seizure signal, relay390 is operated. Relay 390 closes a. circuit for operating relay 385.Relay 385 closes a circuit for operating the slow-to-operate relay 386and closes a circuit from ground at the back contact of relay 386, outerfront contact of relay 390, inner upper front contact of relay 385, backcontacts of relays I58 and I60 of the associated outgoing trunk circuit,conductor I95, back contacts of relays 3 I 5 and 324, lower back contactof relay 302, to the winding of relay 300. The operation of relay 300opens the normally closed operating circuit through the winding ofslow-to-release relay 320 and closes a circuit for operating relay 30]and relay 225 of the associated toll route selector 'IS2. The circuitfor operating relays 30! and 225 is traced from ground at the backcontact of relay 385, outer front contact of relay 390, inner upperfront contact of relay 335, back contacts of relays I58 and We,conductor I55, back contacts of relays M and 325., winding of relay 30!,a back contact of relay 315, back contact of relay 324, Winding ofmarginal relay 3%, a front contact of realy 355, thence in simplexthrough resistors 32! and 322, windings of relays 305 and 323, backcontacts of relay Ilil, windings or retard coil I89, conductors WI andS82, front contacts of relay 354i, conductors 22! and 222, resistors 23land 232, and thence through resistor 230 and the winding of relay 225.Being marginal, relay 355 does not operate. Relay 35E closes a circuitfor operating slow-to-release relay 302. After relay 352 operates, relay3% is held operated in series with resistor 5255 under control of bothof relays till and 552. The operation of relay 302 closes a lockingcircuit for relay 385 and connects ground at the back Contact of relay3H5 to sleeve conductor 223 of the associated selector T82 to controlthe release of this and succeeding selectors. Being slow in operating,relay 355 does not open its back contact until after the seizure signalis ended and relay 3% has released. When relay 390 releases, it connectsground through its back contact and the inner upper front contact ofrelay 335 to hold relays 2m and 225 operated. Relay 302 also closes acircuit for operating the slow-to-release relay 325. The slow-to-releaserelay 32B is normally operated, short-circuiting resistor 322 so that atthe time relay 3% operates, the simplex is unbalanced and the currentthrough the lower windings of the polarized differential relays 3% and323 is larger than the current through the upper windings. Relay 385 isthereby energized in a direction to maintain its armature in normalposition but relay 323 is energized in a direction which operates itsarmature to its alternate position. When relay 325 releases due to theoperation of relay 35%], the short circuit around resistor 322 is openedcausing the release of relay 323. Since relay 322i releases before theslow-to-operate relay 325 has operated, relay 324 also releases. Theaforementioned operation of relay to: also opens a normally closedcircuit through resistor the winding of relay 359 and the upper windingof relay 387. Relay 3l5 is thus normally operated but relay 301, beingmarginal, does not operate. After 1' lay 302 operates, relay 359 is heldoperated in series with conductor 22 and resistor 220.

When signaling relay responds to the first train of dial impulses ofvoice frequency current incoming over trunk T5, relays it'll and 225 arealternately released and reoperated. Slow-torelease relay 302 remainsoperated during the response of relay 551i. The selector TSZ is operatedas hereinhefore described to select the desired group and an idle trunktherein whereupon the operation of relay 22$ extends the connection tothe selected auxiliary toll route selector ASE. The selector A822thereupon controlled hy the response of relay 358! to the second trainof impulses incoming over trunk T5 to select a desired trunk group andupon seizure of an idle trunk in the selected group the connection isextended thereto.

If the selected trunk is an incoming trunk circuit such as 1T2, theoperation is similar to that hereinbeiore described on the call incomingover trunk TI to trunk circuit 1T2. Relay 301 is operated and relay 3I9held operated in series with the lower winding of relay 255 of trunkcircuit 1T2. Relay 351 looks under control of relay 302 and opens thenormally closed circuit for operating pad control relay 333. When thecall is answered the connection of ground to conductor 244 causes therelease of relay 319 and operation of answering supervisory relay 3i l.Relay 3H closes a circuit for operating relay 381 of the signalingcircuit S05. Relay 33'! closes a circuit for operating theslow-to-operate relay 588. After relay 38l operates and until relay 388operates, a circuit is closed for operating relay 389. While relay 389is operated, the source of signaling current VF is connected to theconductors of trunk T5 to transmit an answering supervisory signal tothe calling oflice. If the connection is extended through a cord C2 to atributary line or trunk, the simplex circuit is unbalanced to cause theoperation of the polarized differential relay 355; but if the connectionis extended through cord C2 to a toll line, the simplex is balanced andrelay 355 does not operate. If relay 355 operates, relay 383 is heldoperated and the transmission pads remain in the connection; but ifrelay 355 does not operate, relay 383 releases and relay 384 operates toshort-circuit the transmission pads. Bering signals may be trans mittedover trunk T5 in both directions. If a rering signal is transmitted fromthe calling office, the momentary operation of relay 399 in responsethereto causes the momentary release of relays 3i)! and 255i; but relay3!!!! releases and relay 3M reoperates before relay 352 releases, andtherefore relay 352 holds relays 385 and 385 operated. If an answeringoperator transmits a rering signal, the supervisory relay 3| l ismomentarily released thus eifecting the momentary release of relay 381and momentary operation of relay 389 to connect source VF to trunk T5.Relay 388 is slow in releasing and remains operated; and, when relay 381reoperates, relay 339 releases. If the answering operator disconnectsbefore the calling operator disconnects, the release of relays 212 and213 of the trunk circuit 1T2 causes the operation of relay 255, therebyconnecting battery to both conductors of the simplex to cause theoperation of marginal relay 305 of the calling two-way trunk circuitTWT5. The operation of relay 3B6 closes a circuit for operating relay3H5. Relay 3I6 locks under control of relay 352, closes holding circuitsfor relays 335 and 31 l, opens the simplex circuit to release relays35!, 506 and 25!, and disconnects holding ground potential fromconductor 223 to cause the release of the associated toll route selectorand the release of the auxiliary toll route selector A52 through whichthe connection with trunk circuit 1T2 was established and to cause thetrunk circuit 1T2 to be restored to normal. The release of relay 3t!causes the release of relay 352 and the release of relay 352 causes therelease of relays 3H5, 351 and 3| I. The release of relay 3i 1 causesthe release of relays 381 and 388 and momentary operation of relay 389to send a disconnect signal to the calling ofiice. The release of relay3 l 6 recloses the circuit for operating relay 35! of the trunk circuitand relay 225 of the associated toll route selector. Relay am reoperatesrelay 352 before relays 325 and 325 have both released so that relay 385is held operated and the signaling circuit S05 is ready to repeat thedial impulses of another called route number to selector TS2 andan-auxiliary selector A82 seized by the calling operator. Since relay308 is slower to release than to operate, the disconnect signal is oflonger duration than a seizure signal, When a disconnect signal isreceived over trunk T from the calling ofiice, relay 390 is operated fora long enough time to cause the release of relay 25| and both of relays30I and 302. The release of relay 302 causes the release of relays 385and 386, the release of selectors T82 and A82, and the release of thetrunk circuit 1T2.

If on the call incoming over trunk T5, the selected auxiliary toll routeselector AS2 is operated to extend the connection to a two-Way intertolltrunk circuit such as TWT2, the operation of circuits TWT5 and SC5 aresimilar to the operations above described on a call to trunk circuitIT2.

Assume next that the two-Way trunk circuit "I'WT5 is selected and seizedby an auxiliary toll route selector AS2 on a call incoming over a trunk,such as TI, arranged for composite signaling. In thi case, holdingground is connected from circuit TWT2, through sleeve conductors 223,I93 and 393 to operate relay 3|5 of trunk circuit TW'I5 and to guardagainst seizure of the selected trunk by another selector. Relay 3I5locks directly to conductor 393 and causes the release of the normallyoperated relay 320. Relay 3|! of trunk circuit TWT5 is operated by thecurrent in a circuit from battery through its lower winding, lower backcontact of relay 3I8, conductor 394, through selector ASZ, brush 238 andconductor 224 of the selector TS2, back contact and winding of relay 2|9of the two-way trunk circuit 'I'WT2 of the calling trunk TI and throughthe upper winding of relay 20! to ground. Relay 201 is also operated bythe current in this circuit and relay 2 I 9 is held operated. Relay 3|!locks through its upper winding to holding ground potential on conductor393; and relay 20! locks through its lower winding under control ofrelay 202. With relay 3|! operated, the circuit for operating relay 383is opened, relay 383 releases, relay 384 operates and the transmissionpads are short circuited. The operation of relay 201 places pad controlrelay I83 under control of relay 205. Another circuit. closed uponseizure of the trunk circu t 'I'WT5. is traced from battery through thewinding of relay 3|0. a back contact of relay 300, thence in simplexthrou h res stors 32I and 322, both windings of the difierential andoppositelypoled polarized relays 305 and 323,.throuah back contacts ofrelay IGI and windings of the retard coil I of the outgoing trunkcircuit 0T2 associated with trunk T5, through back contacts of relay300. conductors 39! and 392, talking conductors of selectors ASZ andTSZ. conductors 22! and 222. front contacts of relay 280, conductors I8Iand I82, windings of retard coil I80 and back contacts of relay IBI ofthe out oing trunk circult 0T2 associated with the calling trunk, bothwindings of relay 205. conductor I96. front contact of relay 200,winding of relay 205, back contact of relay 2| Ii, winding of relay2III, back contact of relay 2 I5, conduct-or I95, front contact of relayI56, back contact of relay I58, to round at the front contact ofsignaling relay I90. Re- 1ay 20I is held operated and relay 3I0 isoperated by the current in this circuit. At the time this circuit isfirst closed. the simplex i unbalanced because resistor 322 isshort-circuited by the normally operated relay 320; and for this reasonrelay 323 may be momentarily operated.

without trunk T5 having been released and re- The momentary operation ofrelay 323 may cause the operation of relay 324 but relay 324 cannot locksince relay 325 is not operated. When the short circuit around resistor322 is opened by the release of slow-to-release relay 320, the simplexis balanced and relays 323 and 324 release. Relays 205 and 305 do notoperate because the difiere-ntial energization of these polarized relaysbefore the simplex is balanced is in a direction to maintain thearmatures in normal position. With relay 205 normal and relay 20!operated, pad control relay I83 releases, relay I84 operates and pads P3and P4 are short-circuited. The aforementioned operation of relay 3I0upon seizure of trunk circuit TWT5 closes a circuit from battery throughresistor "5 of the associated outgoing trunk circuit, back contact ofrelay 324, front contact of relay 3I0, back contact of relay I70 oftheoutgoing trunk circuit, and winding or relay 38!. Relay 38! operatesclosing circuits for operating relays 388 and 389. Relay 389 connectssignaling source VF to trunk T5 to transmit a seizure signal. Whenslow-tooperate relay 38B operates, relay 389 releases. When an answeringsignal is received over trunk T5, relay 390 operates closing the circuitfor operating relay 385. Relay 385 locks to ground at a front contact ofrelay 3I5 and closes a circuit for operating sloW-to-operate relay 388.With relays 390 and 385 operated and before relay 386 operates, groundis connected through a back contact of relay 386, front contacts ofrelays 390 and 385, a back contact of relay I58 and a front contact ofrelay I58 of the associated outgoing trunk circuit and through a frontcontact of relay 3I5 to the winding of relay 3I8. After relay 390releases at the end of the answering signal, ground is connected througha back contact of relay 390 and a front contact of relay 385 thence tothe Winding of relay 3I8. Relay 3 I8 operates and locks to the holdingground con nected to conductor 393. With relay 3I-8 operated, the groundat the back contact of relay 390 is further connected through the lowerfront contact of relay 3I8, conductor 394, through selectors A82 and T82to conductor 224, thereby releasing relay 2I9. The release of relay 2I9extends the supervisory ground through conduc tor 224 and a back contactof relay 2I9, to the winding of relay 2| I. Relay 2 is operated by thecurrent in this circuit to transmit an answering supervisory signal overthe calling trunk as hereinbefore described. If a rering signal isreceived over the calling trunk, the momentary release of relay I causesthe momentary release of relays 20I, 3I0 and 38! and relay 339 ismomentarily operated to connect source VF to trunk T5 to transmit arering signal. If a rering signal is received over trunk T5, relay 390 qis momentarily operated, causing the momentary release of relay 2| I;and relay 2 II transmits the rering signal over trunk TI as hereinbeforedescribed. If relay 390 is operated by a disconnect signal incoming overtrunk T5, relay 2| I i released in like manner to send a disconnectsignal over trunk TI. When a disconnect signal is received over thecalling trunk TI, the release of relay I90 causes the release of relay3I0 and the release of both of relays 20| and 202 thereby disconnectingholding ground from conductors 223 and 393 to cause the release switchesTS2 and A82 and return of trunk circuit TWTZ to normal as hereinbeforedescribed. The disconnection of ground from conductor 393, causes therelease of relays 3|5, 3|! and 3I8, and the release of relay 301, ifoperated. The release of relay 3H] causes the release of relays 3t! and388. After relay 381 releases and before the slow-torelease relay 388releases, relay 389 is momentarily operated to connect source VF totrunk T5 to transmit a disconnect signal.

Assume next that the two-way trunk circuit TWT5 is selected by anauxiliary selector AM on a call incoming over another voice frequencyintertoll trunk similar to T5, through a signaling circuit and two-Waytrunk circuit similar to the signaling circuit S05 and trunk circuitTWT5. The signaling and two-way trunk circuits associated with the trunkfrom the calling toll oiiice are hereinafter referred to as the callingcircuits and the signaling and two-way trunk circuits associated withthe trunk to th called toll oilice are referred to as the calledcircuits. The operations of the calling signaling and two-Way trunkcircuits are similar to those hereinbefore described on a call incomingover trunk T5 except as hereinafter mentioned; and the operations of thecalled trunk and signaling circuits are similar to those hereinbeforedescribed when these circuits are seized on a call incoming over a trunkTI except as hereinafter mentioned. Al though at the time of seizur oftrunk circuit TWTB, the resistor 322 of the calling trunk circuit is notshort-circuited, the resistor 322 of the called trunk circuit isshort-circuited by a back contact of the normally operated relay 32!].Therefore, the simplex is unbalanced and not only relay 3!!! of thecalled trunk circuit operates but relay 323 in each of the connectedtwo-way trunk circuits is operated. The opera tion of relay M ii of thecalled trunk circuit causes the operation of relays 381 and 389 tomomentarily connect source VF to trunk T5 to transmit a seizure signal.When the normally operated relay 320 of the called trunk circuitreleases and opens the short circuit around resistor 322, the simplex isbalanced and relay 323 of each trunk circuit releases. The release ofrelay 323 of the called trunk circuit causes the release of relay 324since relay 3l5 is operated on an outgoing call; but in the callingtrunk circuit relay 324 is locked to a front contact of the then alreadyoperated relay 325. With relay 324 of the calling trunk circuitoperated, the operating circuit of relay 3!)! is opened but relay 302 isheld operated through a front contact of relay 324 and a back contact ofrelay 3| 5, thence to ground in the associated signaling circuit ashereinbefore traced. Relay 324 of the calling trunk circuit alsoconnects ground through the windin of relay 3H6 and uppermost frontcontact of relay 309 to resistors 32! and 322 to maintain closure of thesimplex so as to hold relay 3! [I of the called trunk circuit operated.When relay 390 of the called signaling circuit is operated by ananswering supervisory signal from the called toll oflice, it causes theoperation of relay 5H8 of the called trunk circuit and causes therelease of relay 3H! and operation of relay 3!! of the calling trunkcircuit; but, since relay 324 is operated, the operation of relay 3H isineffective to cause the operation of relays 381 and 3891 The voicefrequency answering signal, rering signals, and a disconnect signal fromthe called office are transmitted through the talking connection to thecalling intertoll trunk. The operation of relay 390 of the calledsignaling circuit in response to rering or disconnect signals from thecalled ofilce causes the operation of relay 3 without causing theoperation of relays 38! and 389.

Rering signals received from the calling omce are transmitted throughthe talking connection to the called intertoll trunk. The operation ofrelay 390 of the calling signaling circuit in response to a ringingsignal from the calling office, causes the momentary opening of theholding circuit for relay 302' of the calling two-way trunk circuit butrelay 302 is slow-in-releasing and remains operated. A disconnect signalfrom the calling toll office is transmitted through the talkingconnection to the called toll ofiice and also causes the operation ofrelay 390 of the calling signaling circuit for a long enough interval tocause the release of relay 392, The release of relay 302 of the callingtrunk circuit causes the release of relay 300 of the calling trunkcircuit and release of relay 3H1 of the called trunk circuit. All of thecircuits and switches involved in the connection between the calling andcalled intertoll trunks are thereupon restored to normal.

What is claimed is:

1. In. a telephone system, an incoming line, outgoing lines, meansincluding a selector switch for connecting said incoming line to any oneof said outgoing lines, a differential relay associated with saidincoming line, a simplex circuit including the windings of said relayand the talking con.- ductors or" aid selector, signal receiving meansfor repeat g signals from the incoming line over said simplex circuit toa selected outgoing line, and signaling means associated with saidoutgoing line for unbalancing the simplex circuit to operate said(inferential relay.

2. In a telephone system, an incoming line, outgoing lines, meansincluding a selector switch for connecting said incoming line toany oneof said outgoing lines, two polarized differential relays associatedwith said incoming line, a simplex circuit including the windings ofsaid relays and the talking conductors of said selector, signalreceiving means for repeating signals from the incoming line over saidsimplex circuit to a selected outgoing line, signaling means associatedwith said outgoing line for decreasing the resistance of one side of aidsimplex circuit to cause the operation of one of said polarizeddifferential relays, and signaling means associated with said outgoingline for reducing the resistance of the other side of said simplexcircuit to cause the operation of the other of said polarizeddifierential relays.

3. In a telephone system, an incoming line, outgoing lines, meansincluding a selector switch for connecting said incoming line to any oneof said outgoing lines, a marginal relay and a differential relayassociated with said incoming line, a simplex circuit including theWinding of said marginal relay and windings of said diiTerential relayin series with the talking conductors of said selector, signal receivingmeans for repeating signals from the incoming line over said simplexcircuit to a selected outgoing line, signaling means associated withsaid outgoing line for decreasing the resistance of one side ofsaidsimplex circuit to cause the operation of said difierential relay, andsignaling means associated with said outgoing line for decreasing theresistance of said simplex circuit to cause the operation of saidmarginal relay.

4. In a telephone system, an incoming line, signal receiving meansassociated with said line, a route selector comprisingtalkingconductors, a sieeve conductor and a fourth conductor, groups ofoutgoing lines accessible to said se lector, a simplex circuit includingsaid talking conductors for repeating directive signals re-

